“…Face detection is fundamental in that it serves as the basis for many applications [1] that involve the human face, such as face alignment [2,3], face recognition/authentication [4,5,6,7], face tracking and tagging [8], etc. Face detection is a hard problem because unlike face localization, no assumptions can be made regarding whether any faces are located within an image [9,10]. Moreover, faces vary widely based on gender, age, facial expressions, and race, and can dramatically change in appearance depending on such environmental conditions as illumination, pose (out-of-plane rotation), orientation (in-plane rotation), scale, and degree of occlusion and background complexity.…”